1. Field of the Invention
The invention relates to a method and an arrangement for producing hot-rolled steel strip from continuously cast semi-finished steel in directly successive work steps.
2. Description of the Prior Art
Steel strip is produced by the deformation of, for example, a cast semi-finished steel, whose weight depends on the coil weight of the finished product, to the desired geometric dimensions in one or more rolling processes. The casting and deformation processes usually occur discontinuously not successively. However, such sequential processes entail long processing times, expensive rolling devices and significant energy losses during processing. Moreover, the discontinuous operation results in output and quality losses.
A number of completely continuous cast-rolling arrangements are mentioned in the literature. However, it is always noted that these configurations are not practically applicable, because the final rolling temperatures needed to establish the desired hot-strip properties cannot be reached with such machines. Due to their low casting speed, the strip would cool so quickly that operation without intermediate heating would be impossible, while operation with the required expensive heating units would not be economical.
An arrangement and a process for the continuous production of strip steel or sheet steel from continuously cast flat products is known from WO-A-89/11363. In this prior art arrangement and process, a continuously cast thin slab, after reduction in a first roll pass, is subjected to induction heating and, directly thereafter, is rolled in a multi-stand finishing train into a strip, which is coiled up at the end of the finishing train. This known solution does not disclose details of temperature control with the goal of always ensuring that the finish-rolling of the strip occurs in the austenitic temperature range.
In producing hot strip, the strict restriction that products be finish-rolled in the austenitic range (.gtoreq.880.degree. C.) makes the selection of suitable casting parameters especially important. Casting thickness and casting speed play an important role, because they determine the temperature control throughout the entire arrangement during operation.